Fixes #300 - Adds "get this app in your city link"

- Adds link in footer for directing users to github repository and
ohanapi.org.
- Adjusts padding of paragraphs in footer to only add padding on the
top so as to not double up padding against each other.
- Removes “This website is a” text from footer as the current website
is implied.
- Wraps the google translate drop-down in a paragraph element so that
it participates in paragraph-applied styling in the footer.
Adds test expectation for footer links
Adds homepage spec and removes support method

- Adds functional spec for homepage content.
- Removes looks_like_homepage expectation method from session_helpers
to conform with best practices.
- In pages_spec, converts “should” expectation syntax to “to” syntax to
conform with best practices on betterspecs.org.
Refactors tests

Increases granularity of homepage content specs and converts “should”
syntax tests to “to” syntax tests, per recommendations of
http://betterspecs.org.
Merge pull request #352 from codeforamerica/300-add-get-link

Fixes #300 - Adds "get this app in your city link"